Conductive polymers in their pure state have limited application because their lack of solubility and fusability renders them unprocessable by the conventional techniques of polymer processing: solution-casting and melt-processing. In the recent past, a number of alternative methods have been proposed for producing conductive polymers with improved processability.
U.S. Pat. No. 4,959,162 to Armes discloses processable electrically conductive compositions comprising colloidal particles of an oxidized, polymerizable aromatic heterocyclic monomer, a stabilizing effective amount of a vinyl-pyridine-containing polymer, and dopant ions.
Improving the processability of conductive polymers by compositing them with processable but non-conducting polymers has been the object of a number of inventions. U.S. Pat. No. 5,061,401 to Wernert achieved a processable composite containing a conducting polymer and a thermoplastic polymer substituted with sulfated alcohol groups. Monomer and substituted thermoplastic polymer were dissolved in polypropylene carbonate. Polymerization of the monomer was achieved electrochemically. U.S. Pat. No. 5,028,354 to Smith discloses a processable conducting polymer composite. The composite is formed by first casting a substrate from a solution containing a non-conducting but processable host polymer and a polymerization catalyst, treating said substrate so as to cause gelation of the host polymer, and exposing the gelled substrate to monomer vapor, thereby causing polymerization of the monomer on the surface and in the interior of the substrate.
Another technique common in the prior art for the formation of a conductive composite comprising a conductive polymer and a nonconductive processable host polymer involves the polymerization of conductive polymer on or in a preformed host polymer substrate. U.S. Pat. No. 4,699,804 to Miyata teaches that contacting a monomer solution with a host polymer substrate impregnated with polymerization catalyst, results in polymerization of the monomer on the surface and, to some degree, in the interior region near the surface of the substrate. U.S. Pat Nos. 4,696,835 to Maus and Des. 3,940,732 to Naarman teach that conductive polymers may be deposited on preformed polymeric substrates by first treating the surface of the substrate with a suitable polymerization catalyst and then exposing the treated surface to monomer vapor or to a solution containing monomer. U.S. Pat. No. 4,636,430 to Moehwald and U.S. Pat. No. 4,582,575 to Klivans each teach that the processable conductive polymers can be formed by impregnating a host polymeric substrate with a monomer and polymerizing the monomer electrochemically.
"Polypyrrrole Conductive Composites Prepared by Coprecipitation" by Ruckenstein et al, Polymer, 32, 1991, pages 1230-1235, reported a uniformly distributed polypyrrole-polyurethane composite polymer formed by coprecipitation from a concentrated emulsion comprising polyurethane and an aqueous suspension of polypyrrole powder.
"An Emulsion Pathway to Electrically Conductive Polyaniline-Polystyrene Composites", by Ruckenstein et al., Synthetic Metals, March 1993, pages 283-293, discloses a uniformly distributed polyaniline-polystyrene composite formed by adding an aqueous solution of HCl containing an oxidant to an emulsion comprising a surfactant dissolved in water in the continuous phase, and in the dispersed phase, a mixture of aniline and polystyrene dissolved in an organic solvent.